Oncostatin M (OSM) and Interleukin-31 (IL-31) are members of the IL-6 superfamily and share a receptor subunit, oncostatin M receptor-β (OSMR) (Dillon et al., Nat. Immunol. 5(7): 752-60, 2004). All of the members of this family, except IL-31, share the common chain of glycoprotein 130 (gp130) in their multimeric receptor complexes. OSM signals through a heterodimeric receptor complex containing OSMR and gp130, while IL-31 utilizes a gp130-like receptor, IL-31R, in combination with OSMR (Dillon et al., supra; Dreuw et al., J. Biol. Chem. 279(34): 36112-20, 2004). In general, OSMR and gp130 are expressed fairly ubiquitously across tissues and cell types, and can be induced under a variety of stimulation conditions. IL-31R expression appears to be relatively more restricted and tightly regulated. In human and mice alike, IL-31R mRNA expression is detectable at low levels in tissues such as trachea, skeletal muscle, thymus and bone marrow (Dillon et al., supra). Although the level of expression is starkly different, both IL-31R and OSMR are co-expressed on a multitude of tissues, including skin and intestinal epithelial cells, suggesting those tissues should respond to IL-31 (Dillon et al., supra; Dambacher et al., Gut 56(9): 1257-65, 2007). While OSMR is expressed constitutively in the lung on epithelial cells, IL-31R expression is at negligible to low levels in the lung tissue, but upregulated upon various methods of airway challenge (Dillon et al., supra; Jawa et al., J. Interferon Cytokine Res. 28(4): 207-19, 2008).
Secreted primarily by T lymphocytes, macrophages, and neutrophils, OSM and IL-31 are both upregulated in a variety of disease states that involve inflammation. OSM has been implicated in diverse biological roles including bone formation, cartilage degradation, cholesterol uptake, pain and inflammation (Cawston et al., Arthritis Rheum. 41(10):1760-71, 1998; Hasegawa et al., Rheumatology (Oxford) 38(7): 612-7, 1999; Levy et al., J. Hepatol. 32(2): 218-26, 2000; Manicourt et al., Arthritis. Rheum. 43(2): 281-8, 2000; de Hooge et al., Am J. Pathol. 160(5): 1733-43, 2002; Luzina et al., Arthritis Rheum 48(8): 2262-74, 2003; Morikawa et al., J. Neurosci. 24(8): 1941-7, 2004; Kong et al., J. Lipid Res. 46(6): 1163-71, 2005). OSM has been demonstrated to be a potent modulator of extracellular matrix (ECM) in a variety of contexts, suggesting that OSM is able to mediate seemingly opposite pathological consequences, including fibrosis (an excess of ECM) and cartilage degradation (a breakdown of ECM). Depending on tissue type and environmental milieu, both of these effects have been observed when OSM has been overexpressed or exogenously administered into lungs or joints of mice, respectively (Richards et al., Biochem. Soc. Trans. 30(2): 107-11, 2002; Hui et al., Arthritis Rheum. 48(12): 3404-18, 2003; Rowan et al., Am. J. Pathol. 162(6): 1975-84, 2003). In addition, OSM has previously been shown to be upregulated in human pathologies where these types of consequences exist (Cawston et al., supra; Hasegawa et al., supra; Levy et al., supra; Manicourt et al., supra; Luzina et al., supra). Predominantly, a locally-acting cytokine, OSM is upregulated in the synovial fluid from joints of patients with rheumatoid arthritis (RA) (Cawston et al., supra; Manicourt et al., supra), in the broncheoalevolar lavage (BAL) fluid of patients with scleroderma-associated interstitial lung disease (Luzina et al., supra), idiopathic pulmonary fibrosis (IPF), and in the livers of patients with cirrhosis (Levy et al., supra). The proposed impact on ECM by OSM can be attributed in part to the ability of OSM to shift the balance between matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs). TIMPs bind to MMPs in a 1:1 ratio with a high affinity that results in a loss of MMP proteolytic activity. TIMP-1 and TIMP-3 have been previously shown to be differentially regulated by OSM, resulting in an increase in TIMP-1 and a decrease in TIMP-3 (Gatsios et al., Eur. J. Biochem. 241(1): 56-63, 1996). In addition to regulating the digestion of extracellular matrix components, MMPs are also implicated in the cleaving and subsequent activation of a number of proteins, including TGF-β, a potent pro-fibrotic cytokine (Leask et al., FASEB J. 18(7): 816-27, 2004). OSM has also been reported to be capable of directly inducing the transcription of type I collagen in vitro (Hasegawa et al., J. Rheumatol. 25(2): 308-13, 1998).
Expression of both OSM and IL-31 has been found in the skin of patients with psoriasis and atopic dermatitis, and mutations in OSMR and IL-31R have been linked to systemic cutaneous amyloidosis. System-wide transgenic overexpression of IL-31 induced a pruritic inflammatory response in the skin of mice. Both OSM and IL-31 both signal through OSMR on neurons where they have been suggested to promote nociceptive and pruritic responses.
Collectively, these links to human diseases and the ability of OSM and IL-31 to promote a diverse array of pathologies, including at least inflammation, extracellular matrix remodeling, pain, and pruritis, suggest blockade of OSMR is a useful target for therapeutic intervention in many diseases and disorders associated with OSMR.